1. Field of the Invention
This invention generally relates to attachment of spokes to a bicycle rim. More specifically, the present invention relates to spoke attachment structures for attaching tensioned spokes to a bicycle rim.
2. Background Information
Bicycle wheels are continually undergoing design modifications to make them easier to manufacture and assemble, as well as stronger, lighter and more aerodynamic. Various types of bicycle wheels are being sold on the market at present. Many bicycle wheels include a hub, a plurality of spokes and an annular rim. The hub is rotatably mounted to a part of the bicycle frame. The inner end of each spoke is connected to the hub and the spokes extend outward from the hub. The annular rim is connected to the outer ends of the spokes and includes an outer circumferential part that supports a pneumatic tire.
In general, the spokes of a bicycle wheel are thin wire spokes. A flange that connects the spokes to the hub is normally formed at both ends of the hub. Specifically, for example, holes are formed in the hub flanges for receiving the inner ends of the spokes. The interior end of each spoke is supported in a hole formed in one hub flange. In general, the outer end of each spoke is threaded such that the outer end can engage with a spoke nipple that secures the outer end of the wire spoke to the rim hole. By turning the spoke nipples, the tension in the spokes can be adjusted to the proper tension. However, sometimes during riding, the threaded connection between the spoke nipple and the outer end of the wire spoke can loosen such that slack (i.e., reduced tension) can occur in the spokes. To prevent of slack from occurring in the spokes, spoke attachment structures have been developed with a portion having increased friction. One example of such a spoke attachment structure is disclosed in U.S. Pat. No. 7,137,671 in which a plastic ring is disposed inside of a spoke attachment element for engaging the thread of the spoke. Another example of such a spoke attachment structure is disclosed in European Patent Publication No. 1,101,631 in which a friction portion is located in the threaded portion of a spoke attachment element. While these spoke attachment structures might be able to prevent slack (i.e., reduced tension) from occurring in the spokes, these spoke attachment structures can be difficult and/or costly to manufacture.